I would have to agree that the one site that took the biggest hit (it has dropped out of the first 90 for all keywords) is anything but over optimized. I can understand movement, but dropping off the face of Google for all keywords?

An interesting point to note is that there is another URL that does a serverside rediret to this main site. This URL is ranking for two keywords on Google. You would think that if it were a site problem, the secondary URL would face the same drop. However, the secondary URL never had the same good ranking that the main site used to have. It still just ranked for these same two keywords.

Interesting.